Dicyanate monomers

Richard B. Graver of Interez Inc., formerly Celanese Specialty Resins Division, Celanese Corporation. Both K-353 and the dicyanate monomers were used as received. All the blends were prepared by dissolving completely the components in methylene chloride, and the solvent was subsequently removed by slow evaporation with mild heating. The solid blends were then dried in vacuo at 65-75°C overnight before being subjected to thermal analysis. 

Under the same conditions, the BCB/dicyanate mixtures lost 24-28% of their original weights as opposed to 12% weight loss observed for pure BOB. Although the results were not as good as those with BCB/K-353, it is quite clear there was definitely some interaction, most likely in the Diels-Alder fashion, between BOB and the dicyanate monomers. 

Figure 7. Isothermal aging studies of the thermosetting resins derived from the 1 1 molar mixture of BCB and the dlcyanate monomers, in comparison with those derived from pure BCB and the dicyanate monomers.

We are grateful to the generosity of Hexcel and Interez Corporations for sending us the free samples of K-353 and dicyanate monomers, respectively. We also thank Marlene Houtz and Dr. Ivan J. Goldfarb for their contributions in the thermal analysis, and Prof. R. G. Bass for suggesting bispropynones. 

If flexibilization of the very rigid polytriazine network is desired, monoaryl cyanates are added to the dicyanate monomers. In some patents the use ofp-isopropylphenyl (cumyl) cyanate (Scheme 5) is mentioned. 

Kim et al (1999) examined the morphology and cure of semi-IPN epoxy resin or dicyanate-polyimide/polysulfone-carbon-flbre Aims. Polyimide or polysulfone Aims were inserted into the curing epoxy-dicyanate monomers to form semi-IPNs with sea-island morphology at the thermoset-thermoplastic interface. The final carbon-flbre-thermoplastic-dicyanate Aims had fracture toughness three to five times higher than that of unmodified carbon-flbre-dicyanate composites. 

The study of the interaction mechanism of thin films of BACY prepolymer on different surface states of Si and oxidized Al employing advanced techniques such as XPS, UPS, MIES, IR reflection spectroscopy, and AFM was undertaken by Possart and Dieckhoff [364]. The trioxy triazine was the only moiety identified to have adhesive interaction with the substrate. On a Si surface, the mechanism was identified as donor-acceptor interaction where the lone pairs of electrons on N and O atoms of trioxy triazine were involved in the electron donor process for the Si cation. On aluminum oxide, the Lewis acidic OH groups act as electron acceptors, withdrawing electron density from the lone pairs of O and N of the trioxy triazine. Back donation of electron density from Al metal to the organic layer is operative beneath the oxide layer. The dicyanate monomer doesn t adhere at all and desorbs quickly out of the interphase region on the substrate. It was concluded that thermosetting reaction of the prepolymer is thus hampered and the resulting network will be less dense near the substrate than in the bulk. 

Chart I. Chemical structures and characteristics of dicyanate monomers, elastomer additives, and PES additives. 

Equation 3 is often used in the literature to account for the kinetic behavior of several common dicyanate monomers (25, 26). The autocatalytic character of cyanate polycyclotrimerization is now quite well established we noticed that it was especially enhanced in samples with a large surface directly exposed to air (24, 27, 28). The kinetics of DPEDC blends were more difficult to describe because they were perturbed by several residual impurities in the monomer. Together with adventitious air moisture, the latter increased gel conversion with respect to the theoretical value (0.5). 

With the use of phase diagrams, we are also able to control the temperature and the viscosity at which phase separation occurs. The final morphologies of the three systems based on the same dicyanate monomer and modified with NFBN, ATBN, and PES are quite different and have different interfaces. When the additive can react with the monomer before network formation, a two-level structure is observed a primary structure (dispersed particles), and a substructure inside the dispersed particles. The complex morphology obtained in this case gives the best toughening effect. 

AroCy . [Bhtme-Poulenc] Dicyanate monomers and jHepolymeis co-reacts with and cutes epoxy resins reactive diluent for adhesives, pepiegs laminating resin. 

Cyanate esters are a family of aryl dicyanate monomers that contain the reactive cyanate (-0-C=N) fimctional group. When heated, this cyanate functionality undergoes an exothermic cyclotrimerization reaction to form triazine ring connecting units, resulting in the formation of a thermoset polycyanate polymer. 

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